Rotating welding transformer



April 21, 1964 K. R. KESKA ROTATING WELDING TRANSFORMER 2 Sheets-Sheet 1 Filed May 12, 1961 INVENTOR. KENNETH R. KESKA ATTORNEYS April 2 1964 K. R. KESKA 3,130,291

ROTATING WELDING TRANSFORMER Filed May 12, 1961 2 Sheets-Sheet 2 INVENTOR.

' KENNETH R. KESKA BY ATTORNEYS United States Patent Office 3,130,291 Patented Apr. 21, 1964 3,13tl,2l RQTATRNG WEEQDENG TRANSFORMER Kenneth R. Kesha, Bay Village, Qhio, assignor to The ggder Company, Cleveland, Ohio, a corporation of Filed May 12, 1961, Ser. No. 169,599 4 Qlaims. (til. 219-63) The present improvements, relating as indicated to rotating welding transformers, are more particularly concerned with such transformers of the type in which the welding electrodes are mechanically unite-d directly with the structure serving as the secondary of the transformer.

Such direct physical union of the electrodes and transformer secondary if and when fully realized eliminates the need for separate conductors in the secondary circuit, avoiding the energy' loss in such conductors and of course permitting compact design of the unit. The compactness of the design is one of the concerns of the present invention, with the latter providing a simplified construction for such a transformer using only a small number of major structural components in an extremely compact assembly. As a more specific example, the transformer core and the windings or turns in the new construction are supported at the electrode end or head of the welder in such manner that the secondary is not required to carry load in the mounting and use of the welder and thus the design is not encumbered by such a mechanical consideration.

Another structural factor bearing on the electrical characteristics of the transformer is the nature of the actual support of the secondary, core and primary in proper interrelation in the assembly, and a further obiect of the invention is to provide a mounting of such components which is mechanically improved and essentially troublefree. The secondary in accordance with the invention encloses the core and the primary winding, and the latter are supported in spaced relation by relatively exterior or non-penetrating means. This is in particular contrast to a more conventional mounting scheme requiring insulated core bolts, wherein such bolts are subject to heating, mechanical stress, and other influences which could lead to breakdown of the core bolt insulation and short circuiting of the transformer.

It is also an important object of the present invention to provide improved means for internally cooling the new welding transformer. As already noted, the core-primary sub-assembly is enclosed in spaced relation; the enclosure is both irnperforate and hermetically sealed. The cooling is more particularly accomplished by vaporization of liquid from a charge thereof partially filling the enclosed and sealed void between the core primrary device and the secondary, with the latter serving as the casing. As will appear more fully hereinafter, such vaporization cooiin-g has proved to be extremely efiicient and beneficial, primarily by reason of greater uniformity of the cooling obta-ined. This uniform cooling in the new construction substantially reduces hot spots within the welder, which of course determine the permissible input to the transformer, and there is realized a material gain in capacity with vaporization cooling in accordance with the invention as compared to other expedients, such as circulating a cooling fluid through the structure.

In further contrast to an internal circulating fluid system as commonly used in rotary welders, the vaporization cooling provided in the new welder eliminates the need for internal fluid conduits and passages, rotary fluid supply and discharge connections, external accessories such as heat exchangers, circulating pumps, filters and the like, and all risk attendant upon the transfer of fluid to and from the interior of the transformer. employed for the vaporization cooling will be an inert The liquid and stable dielectric having an appropriate vaporization characteristic for extraction of the heat generated within the transformer, with the construction such that the parts which thus unavoidably become heated are relatively rotated through the liquid charge and the vapor produced is condensed within the unit and returned to the charge.

The hermetic sealing of the structure has the further benefit of protecting the transformer components from environmental fumes, dust and other air borne impurities.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, [of but one of the various ways in which the principle of the invention may be employed.

In said annexed drawings:

FIG. 1 is a side elevation of a welding transformer in accordance with the present invention, with a broken portion thereof in longitudinal section;

FIG. 2 is a sectional View, on an enlarged scale, the plane of which is indicated approximately by the line 22 in FIG. 1; and

FIG. 3 is a similarly enlarged section of the welder, partially fragmented, with the plane of the section indicated by the line 3'3 in FIG. 2.

Referring now to the drawings in detail, the illustrated welder comprises a hollow center shaft 10 supported horizontally and freely for rotation in a front bearing 11 and a rear bearing 12 mounted in blocks l3 land 14 respectively. The bearing blocks are secured to suitable frame structure, not shown, preferably in such manner as to perrnit a degree of vertical adjustment of the horizontal shaft. The shaft projects beyond the bearings at both ends, with a welding head designated generally by reference numeral 15- mounted on the end of the shaft forward of the front bearing 1-11 and a slip ring assembly indicated generally at 16 on the other projecting end of the shafit behind the rear bearing 12,.

The forwardly projecting end of the shaft 10 which supports the welding head is tapered outwardly as shown at 17 and terminates in a reduced and grooved cylindrical seat 18. An inner mounting ring 19 is fitted over such end seat of the shaft and locked thereon by means of interposed insulative cement 2%, which can be one of the synthetic resin adhesives.

A-n electrode support 21 made of copper closely encircles a forward portion of the inner mounting ring 19 and is secured thereto by a plurality of circurnferentially spaced radial keys 22, bridging the joint of the two rings and attached respectively to the same by cap screws 23. An annular casing 24 of general U-shape in crosssection is located on the mounting ring 119 inboard of and generally against the rear face of the electrode support 21, with the latter serving to close the casing. The inner forward edge '25 of the casing 24 abuts and thus is in conductive contact with the opposed inner portion of the electrode support 21, and screws 26 are threaded through the conductor ring into such edge portion of the casing to join the two. The outer edge portion 2 7 of the casing is partially received in a peripheral notch 28 in the rear face of the electrode support 21, and electrical insulation 29 is interposed between these portions, with further screws Sill passed through the conductor ring into the casing. These outer screws 31 are insulated electrically from the support 21 by means of insulative spacers 31 about the shanks of the same and insulating washers 62 about the heads in recesses formed therefor in the outer face of the support 21. Each such recess is, moreover, closed by an insulating plug 3-3.

The casing 24 is made of copper and constitutes the secondary of the welding transformer. Such transformer is completed by a unitary core-primary assembly comprising a laminated iron core 34 in ribbon wound form and a primary coil 35 wrapped thereabout in one or more layers. This toroidal assembly is housed in spaced relation within the secondary 24, with a number of insulative rings as disposed at three sides between the primary winding 35 and the respectively opposed inner surfaces of the secondary casing. Several core drive keys 37 made of copper are brazed in peripheral openings in the secondary and fit into keyways in the outer insulating ring of the core-primary assembly to locate and hold the same in the proper spaced relation.

The outer edge portion 27 of the secondary 24 is formed with a flange 38, while an electrode collar 39 is seated in spaced opposition in a groove provided in the periphery of the electrode support 21. Such collar comprises two semi-circular pieces joined at their ends by non-magnetic screws 4%. An inner electrode 41, also in the form of a ring, is disposed against the flange 38 of the secondary and secured thereto by means of screws 42. A corresponding outer electrode 43 is mounted on the conductor ring against the electrode collar 39, with screws 44 attaching the same to the collar. The electrodes, of the same diameter, are of course spaced slightly apart at their respectively inner and opposed faces, and a seal gasket 45 is placed between such faces of the electrodes about the insulation 29 separating the outer edge portion 27 of the secondary 24 and the support 21.

Two copper terminal pins 46 and 47 extend through close-spaced transverse openings in the support 21, within insulative spacing and fluid sealing connections 48, and are electrically connected at their inner ends to the ends of the primary winding 35 within the secondary casing. At their outer ends, these pins are clamped respectively in copper conductor bar devices 49 and 50 which extend inwardly over the open end of the center shaft 10. A first insulating pad 51 is placed between such bars and the outer face of the conductor 21 where the terminals 46 and 4-? emerge from the latter, while a second insulating pad 52 is disposed between the inner end portions of the bars. A pair of insulated conductors 53 is clamped, by a block 54 and screws 55, to the inner end portion of the bar as and extends therefrom rearwardly through the shaft. Another pair of similar conductors 56 is connected to the other terminal bar 47 by block 57 and screws i, and also extends through the interior of the hollow center shaft. lnsulative spacer rings 59 center the conductors within the shaft.

The conductors 53 extend to the rear of the shaft and, passing through the wall of the same, are both connected to a copper slip ring so fixed on the shaft but insulated therefrom. Such other end of the hollow shaft is closed by an end plate 61 and slip ring 6t) is spaced inwardly from such plate by an insulative ring 62. A further insulative spacer 63 is disposed about the shaft at the other or forward side of the slip ring 669, and a further copper slip ring 64 is mounted on the shaft against this spacer. The conductors 56 are both connected to this further slip ring 64, whereby the rings 60 and 64 are respectively connected to the ends of the primary transformer winding 35. It is not necessary that plural conductors or wires be employed for each such connection, the conductors shown being of standard available size which should be paired to carry the current applied.

A control slip ring assembly comprising three insulative spacers 65 and two control slip rings 66 and 67 is mounted on the shaft 10 forward of the current supply slip ring 64 in insulated relation. A flanged spacer 68 on the shaft extending from the rear bearing location against the last or forward insulative ring 65 completes this rear terminal section of the welder. As indicated, the slip rings as and 67 are used for a control purpose and insulated wires 69 extend respectively therefrom through the shaft 1% to the head 15 and to connections with a temperature responsive switch 7t) which is sealed in an opening in the conductor ring 21. The inner end of this switch device is received in a cartridge 71 which is thermally but not electrically conductive, against an internal spring 72, and pressed into contact with the primary Winding. The temperature switch is thus responsive to the temperature of the core-primary assembly and is operative to open, or close depending upon the external circuit, at a predetermined maximum safe operating temperature. As will be appreciated, this control makes it possible to interrupt the current supply to the welder in the event that the temperature should for any reason become excessive. Both the current slip rings and the control slip rings will of course be engaged by brushes for energizing the transformer and for connection of the temperature switch in the appropriate external circuit.

The welding head 15 is provided with a moisture tight cover 73, preferably made of aluminum and having an insulating pad 7 against the inner surface of the same, with this cover being attached to the face of the support 21 and enclosing the terminal assemblies and the temperature switch.

it will be seen that the core-primary assembly 34, 35 is completely enclosed by the continuous and imperforate secondary casing 24. Such enclosure is, furthermore, hermetically sealed and, for this purpose, there is a seal ring 75 between the inner edge portion 25 of the secondary 24 and the inner mounting ring 19, another seal ring 76 between such edge portion and the abutting surface of the support 21, and a further sealing ring 77 between the outer edge portion 27 of the secondary and the conductor 21. The thus sealed void between the secondary and the core-primary assembly is partially filled with a liquid 78 suitable for cooling by vaporization and introduced through a normally plugged opening 79 in the secondary casing 24.

The liquid employed for such evaporative cooling will of course have a liquid range properly related to the internal temperature conditions of the Welder in operation for the desired vaporization and consequentextraction of the heat. In addition, it should be inert, dielectric and thermally stable, with one of the available fiuorochemical liquid cooling mediums preferred. One such liquid which can be used is principally isomers of perfluoro cyclic ether having a boiling point of approximately 214 F. and high dielectric strength. The quantity of the liquid used should provide appreciable immersion of the core-winding assembly, preferably on the order of from 25 to 40%, and not exceeding 50%, with such a charge forming a definite liquid bath through which the transformer components are effectively rotated in operation of the welder, it being understood that the electrodes normally roll on moving work, such as a longitudinally advancing tube blank, and hence the welder rotates.

The welder illustrated in the drawings is also provided with a sprocket 8t keyed on and insulated from the shaft 10 between the bearings and a chain 81 thereabout for positive rotation of the assembly by an external drive when desired, for example, to dress or trim the electrodes.

There is not only direct and immediate interconnection of the electrodes 41 and 43 and the electrical ends of the secondary 24 in this construction, the secondary copper is mechanically joined to the center shaft 10 at the electrode side of the unit and therefore does not carry load force. Since the secondary is continuous and imperferate, uniform distribution of the current therein is realized, and the core 34 is both free from penetration by support elements and continuous, that is, without any air gaps therein. This toroidal primary assembly is moreover extremely easy to Wind.

In operation of the new welder, the transformer components are accordingly rotated through an area of contact with the liquid charge, with evaporative cooling and condensation of the vapor in the upper portion of the enclosure. It has been shown by testing that such vapor cooling is effective to eliminate hot spots within the welder. While internally fluid cooled rotary transformers have been made with fairly low average winding temperature in operation, hot spots at substantially higher temperatures occur and these determine the actual or permissible input to the transformer. The hot spot temperature is accordingly the critical factor, and it is in this regard that the vapor cooling provides such marked improvement, since the greater uniformity of the cooling obtained in the latter instance reduces the maximum temperature substantially, for example more than fifty degrees Fahrenheit. This in turn means that the transformer input can be safely materially increased with comparable insulation. As a more particular example, a vapor cooled transformer as illustrated and described can operate at 200 kva., while a conventional water cooled transformer of roughly the same size and using the same insulation materials could not handle more than about 90 kva.

It will also be noted that the secondary 24 is almost entirely exposed for dissipation of heat therein and, in particular, is appreciably spaced outwardly from the center shaft 10. The exposed surface area of the secondary is therefore increased, as compared for example to a drum type of secondary penetrated by the shaft. The sealed nature of the new transformer, moreover, facilitates the application of a cooling medium to the exterior of the same in order to enhance such dissipation of heat from the secondary, normally desired to realize the full operating potential of the unit. The water usually supplied to the electrodes in use of such a welder can, for example, be safely permitted to circulate over the outside of the secondary case as well for such purpose or an auxiliary supply of coolant for the latter can be provided.

There is a further adventage provided by this new construction in the area of maintenance, repair and replacement. Not only can the electrode elements ll and 43 be removed and replaced with obvious ease, the entire head 15, including the transformer assembly, can be readily withdrawn if desired by the relatively simple removal of the cover 73, disconnection of the terminal bars 49 and 50, and freeing of the radial keys 22. The head is then free to be moved axially from the end of the center shaft.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I, therefore, particularly point out and distinctly claim as my invention:

1. In a rotating welding transformer including a shaft and means for supporting the shaft freely for rotation on its axis; a welding head comprising conductor means secured to said shaft and projecting outwardly from about the same, said conductor means including first work-contacting rotary electrode means, a transformer secondary in the form of an annular case of general U-shape in crosssection attached to said conductor means with its open side against and closed by a side of the conductor means, the outer wall surfaces of said annular case being substantially fully exposed to the atmosphere for dissipation of heat therefrom about all sides of the same, one edge portion of the secondary being in conductive contact with the conductor means and the other edge portion insulated therefrom, second rotary electrode means carried by the secondary in electrical connection with the other edge portion of the same and in spaced opposition to the first electrode means, toroidal core and primary winding means in spaced relation within the secondary case, and a charge of liquid dielectric partially filling the space between the toroidal core and primary winding means and the secondary for evaporative cooling of the same in operation of the transformer.

2. In a rotating welding transformer including a shaft and means for supporting the shaft freely for rotation on its axis; a welding head comprising conductor means secured to said shaft and projecting outwardly from about the same, said conductor means including first work-contacting rotary electrode means, a transformer secondary in the form of an annular case of general U-shape in crosssection attached to said conductor means with its open side against and closed by a side of the conductor means, the thus attached secondary case encircling said shaft at an appreciable outward spacing from the same, the inner wall portion of the secondary case being exposed to the atmosphere as a result of such spacing of the case from the shaft for dissipation of heat at this wall portion, one edge portion of the secondary being in conductive contact with the conductor means and the other edge portion insulated therefrom, second rotary electrode means carried by the secondary in electrical connection with the other edge portion of the same and in spaced opposition to the first electrode means, toroidal core and primary Winding means in spaced relation Within the secondary case, and a charge of a liquid dielectric partially filling the space between the toroidal core and primary winding means and the secondary for evaporative cooling of the same in operation of the transformer.

3. In a rotating welding transformer, disc-like conductor means having an outer portion serving as first electrode means, a secondary in the form of an annular case of general U-shape in cross-section having its edge portions secured to a side of said conductor means generally within the outer first electrode portion of the same, whereby the later closes the case, the inner edge of the case being in conductive connection with the conductor means and the outer edge portion insulated from the same, second electrode means carried by the case in conductive connection with said other edge portion and extending outwardly therefrom in spaced opposition to the first electrode means, toroidal core and primary winding means housed in spaced relation within the secondary case, and a charge of a liquid dielectric partially filling the space Within the case about the core and primary winding means for evaporative cooling of the transformer.

4. A rotating welding transformer comprising a shaft, a welding head including a hollow annular enclosure having inner and outer wall portions and end wall portions therebetween, said enclosure further having a circumferential insulative wallsection and being otherwise continuously conductive to form a single-turn secondary Winding, the electrical ends of which occur at the respective sides of said insulative section, first and second electrode means directly connected respectively to such electrical ends of the enclosure and extending therefrom in opposed spaced relation, a toroidal core and primary winding assembly within and spaced from the interior surfaces of said secondary to provide a void between the primary and secondary, a bath of a liquid dielectric cooling medium partially filling said void, said liquid being vaporizable by the heat normally generated within the transformer windings during use, and support means for supporting the welding head on the shaft for rotation of the head as a result of engagement of said electrode means with a moving workpiece, said support means having only limited interengagement between the shaft and the head and the major sections of both the inner and outer Wall portions of the secondary enclosure being exposed to the atmosphere for dissipation of heat therefrom.

(References on following page) Q u- References Cited in the file of this patent 1,691,696 Baum Nov. 13, 1928 UNITED STATES PATENTS 2,179,661 Jones Nov. 14, 1939 2265 627 Caputo Dec. 9 1941 1,478,262 Snodgrass Dec. 18, 1923 1,502,140 Hunter July 22, 1924 5 2,419,837 Elugln APR 1947 1,526,347 Knotis Feb. 17,1925 2,993,109 ludbury y 1961 

1. IN A ROTATING WELDING TRANSFORMER INCLUDING A SHAFT AND MEANS FOR SUPPORTING THE SHAFT FREELY FOR ROTATION ON ITS AXIS; A WELDING HEAD COMPRISING CONDUCTOR MEANS SECURED TO SAID SHAFT AND PROJECTING OUTWARDLY FROM ABOUT THE SAME, SAID CONDUCTOR MEANS INCLUDING FIRST WORK-CONTACTING ROTARY ELECTRODE MEANS, A TRANSFORMER SECONDARY IN THE FORM OF AN ANNULAR CASE OF GENERAL U-SHAPE IN CROSSSECTION ATTACHED TO SAID CONDUCTOR MEANS WITH ITS OPEN SIDE AGAINST AND CLOSED BY A SIDE OF THE CONDUCTOR MEANS, THE OUTER WALL SURFACES OF SAID ANNULAR CASE BEING SUBSTANTIALLY FULLY EXPOSED TO THE ATMOSPHERE FOR DISSIPATION OF HEAT THEREFROM ABOUT ALL SIDES OF THE SAME, ONE EDGE PORTION OF THE SECONDARY BEING IN CONDUCTIVE CONTACT WITH THE CONDUCTOR MEANS AND THE OTHER EDGE PORTION INSULATED THEREFROM, SECOND ROTARY ELECTRODE MEANS CARRIED BY THE SECONDARY IN ELECTRICAL CONNECTION WITH THE OTHER EDGE PORTION OF THE SAME AND IN SPACED OPPOSITION TO THE FIRST ELECTRODE MEANS, TOROIDAL CORE AND PRIMARY WINDING MEANS IN SPACED RELATION WITHIN THE SECONDARY CASE, AND A CHARGE OF LIQUID DIELECTRIC PARTIALLY FILLING THE SPACE BETWEEN THE TOROIDAL CORE AND PRIMARY WINDING MEANS AND THE SECONDARY FOR EVAPORATIVE COOLING OF THE SAME IN OPERATION OF THE TRANSFORMER. 